A tire-pressure gauge, or tyre-pressure gauge, is a

pressure gauge Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressur ...

used to measure the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...

s on a vehicle. Since tires are rated for specific loads at certain pressure, it is important to keep the pressure of the tire at the optimal amount. Tires are rated for their optimal pressure when cold, meaning before the tire has been driven on for the day and allowed to heat up, which ultimately changes the internal pressure of the tire due to the expansion of gases. The precision of a typical mechanical gauge as shown is ±. Higher precision gauges with ± uncertainty can also be obtained.

Tire-pressure monitoring systems

Many modern cars now come with built-in tire

pressure sensor A pressure sensor is a device for pressure measurement of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually act ...

s that allow all four tire pressures to be read simultaneously from inside the car. Before 2005, most on-board

tire-pressure monitoring system A tire-pressure monitoring system (TPMS) monitors the air pressure inside the pneumatic tires on vehicles. A TPMS reports real-time tire-pressure information to the driver, using either a gauge, a pictogram display, or a simple low-pressure wa ...

s (TPMS) used ''indirect'' pressure monitoring. The anti-lock brake sensors detect one tire rotating faster than the rest and indicate a low tire pressure to the driver. The problem with this method was that if tires all lost the same pressure then none would show up against the others to indicate a problem. However, research have shown that both direct and indirect tire pressure monitoring systems are equally effective.

Regulations on tire pressure

Since September 2007 all new automobiles below in weight sold in the United States are required to incorporate a Tire Pressure Monitoring System, which is capable of monitoring all four tires and simultaneously reporting under-inflation of 25 percent of cold placard pressures in any combination of all four tires. TPMS known as

Direct TPMS Direct TPMS, or direct tire pressure monitoring systems (direct sensor TPMS) refers to the use of a pressure sensor directly mounted on the wheels or tires of a vehicle.Hawes, p. 1. The pressure inside the tire is measured using a pressure transd ...

are capable of TREAD Act legislation requiring simultaneous pressure measurement for each tire pressure.http://www.nhtsa.dot.gov/cars/testing/ncap/Tyres/pages/TPandLoading.htm

References

{{Tires, state=collapsed Pressure gauges Tires